Polyatomic Ions

Admit Slip

What is the name for negative ions?

What is the name for positive ions?

Today’s Agenda

Admit Slip Homework Review Notes Classwork Exit Slip

Homework

Homework Review1. Li+1 S-2 Li2S

2. Ca+2 P-3 Ca3P2

3. K+1 N-3 K3N

4. Al+3 P-3 AlP

5. Ga+3 I-1 GaI3

Objectives

You will be able to:Predict the ions that elements will formPredict the ionic compound that two

elements will formUse polyatomic ions to predict compoundsUse ionic compounds to predict mystery

ionsWrite the names of ionic compounds

Polyatomic Ions 11/18/11

Some ions are formed from just one atom (like Ca+2 ) but other ions are made up of a group of atoms.

These ions are called polyatomic ions. Polyatomic means “many atoms”.

Common polyatomic ions include

nitrate NO3-1 , sulfate SO4

-2 ,

carbonate CO3-2 , hydroxide OH- ,

phosphate PO4-3 , ammonium NH4

+1

These are also listed on the back of your periodic table.

Ionic compounds are always written with the metal first. (NaCl)

The names for ionic compounds include the name of the metal atom and then the nonmetal atom with the end changed to -ide.

(Ex. sodium chloride, instead of sodium chlorine). With polyatomic ions, the name of the ionic

compound doesn’t need to be changed.

Examples

Name the following ionic compounds: GaO

MgF2

Cs3PO4

NH4I

Predicting “Mystery” Ions

You can use the ions you know in an ionic compound to predict the ions you don’t know.

For example, the ionic compound XN where X is an unknown atom.

What do you know about the charges in a compound?

They have to cancel out to zero.

XN So if N is -3, then “X” has to be +3. “X” must be an element in the 3rd column.

XO So if O is -2, then “X” has to be +2. “X” must be an element in the 2nd column.

MF2

So if F is -1, then “M” has to be +2. “M” must be an element in the 2nd column.

Classwork

Turn back to your Worksheet and complete the problems and the Exit Slip!

When you are done, work on your homework!